Effect of multi-functional epoxy chain extender on the weathering resistance performance of Poly(butylene adipate-co-terephthalate) (PBAT)

In this research work, both natural weathering and artificial weathering processes were carried out to investigate the effects of multi-functional epoxy chain extender (Joncryl ADR 4370) content on the degradation and the mechanical properties and molecular weight of poly(butylene adipate-co-terephthalate) (PBAT). The carboxyl end-groups of PBAT decreased significantly with an increase in ADR content from 0 to 1.5 wt%. Similarly, the molecular weight of PBAT initially increased and then decreased because of the formation of a crosslinked network structure under the influence of excessive chain extenders. The main degradation mechanism of PBAT during the natural and artificial weathering process is photo-degradation and hydrolyzation. The degradation rate of PBAT increased with increasing content of chain extender, as hydroxyl groups facilitate the water attack on the ester bonds of PBAT. In contrast, the higher content of chain extender presented the lower loss velocity of the tensile strength. This is mainly because the more ADR content, the more crosslinking network structures will be formed during the melting extrusion which can slow down the decrease of tensile strength. Hence, it is indicated that the crosslinking structure has more effect on tensile strength than that of hydrolysis effect during degradation. According to the analysis and study on the performance changes of PBAT/ADR materials under the conditions of long-term natural weathering (360d) and artificial weathering (600 h), this work provides theoretical guidance to produce PBAT mulching films with excellent performance.